Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.71	3.476%	$123.8711	$123.87	$123.85	$123.90
Purchase #2	$141.36	7.308%	$151.6906	$151.69	$151.70	$151.70
Purchase #3	$186.89	7.279%	$200.4937	$200.49	$200.50	$200.50
Purchase #4	$241.37	4.175%	$251.4472	$251.45	$251.45	$251.40
Purchase #5	$57.52	11.442%	$64.1014	$64.10	$64.10	$64.10
Purchase #6	$167.59	11.105%	$186.2009	$186.20	$186.20	$186.20
Purchase #7	$123.33	8.775%	$134.1522	$134.15	$134.15	$134.20
7 purchase totals =	$1,037.77		$1,111.9571	$1,111.95	$1,111.95	$1,112.00